Effects of growth hormone replacement on physical performance and body composition in GH deficient adults

OBJECTIVES Adults with GH deficiency complain frequently of low energy leve ls resulting in a low perceived quality of life. Body composition is altere d, with increased fat mass and decreased lean body mass, and muscle strengt h is reduced. The aims of this study were to determine the effects of GH re placement on physical performance and body composition in GH deficient (GHD ) adults. STUDY DESIGN The study consisted of a 6-month randomised, double-blind, pla cebo controlled study of the administration of GH (0.25 IU/Kg/week (0.125 I U/kg/week for the first four weeks)) followed by a 6-month open phase of GH therapy. PATIENTS Thirty-five GHD adults (17F), mean age 39.8 years (range 21.1-59.9 ), on conventional replacement therapy as required. METHODS Maximum aerobic capacity was measured using an incremental walking test to volitional exhaustion on a motorized treadmill. Quadriceps muscle s trength was assessed by measuring maximum voluntary contractions and body c omposition by dual energy X-ray absorptiometry (DEXA). RESULTS There were no statistically significant changes in quadriceps muscl e strength between the GH and placebo groups. In both groups, there was a s ignificant increase in quadriceps muscle strength compared to baseline duri ng the double-blind period (GH group: P = 0.016; placebo group: P = 0.048). Compared to baseline, muscle strength was further improved in the GH treat ment group after 12 months of treatment (P = 0.007). No further improvement was noted in the placebo group after 6 months on open GH treatment. In the placebo group, maximum aerobic capacity decreased during the placebo perio d (P = 0.017). No significant change was observed in the GH group. During o pen GH treatment the previously placebo treated group had a significant inc rease of maximum aerobic capacity (P < 0.049) whereas no significant improv ement could be seen in the GH group. In the GH group there was a significan t increase in lean body mass (P = 0.001) and a significant decrease in fat mass (P < 0.001). No statistically significant changes were noted in the pl acebo group: the differences in these changes between treatment groups were statistically significant (lean body mass: P = 0.009; fat mass: P < 0.001) . The changes in body composition in the GH group during the 6 month placeb o-controlled period were maintained during continued open treatment. Simila r changes in body composition to those observed in the GH group during the 6 month placebo-controlled period were also seen in the placebo group once the patients received GH treatment. CONCLUSIONS Our data show that GH replacement in GH deficient adults is ass ociated with favourable changes in body composition, which could be importa nt in the long term health outcome and physical activity of GH deficient pa tients. Our data support the concept that GH therapy alone, in the absence of some form of exercise programme, may increase the amount of lean tissue but not the quality or functional capacity of this tissue and it may be tha t training, in addition to GH therapy, may be necessary to significantly in crease physical performance in these patients. We suggest that future trial s with GH therapy and general approaches to the treatment of GH deficiency should include a planned activity programme as an approach to health improv ement in these patients.